FDA Approves Second Growth Factor for the Spine
BY ROBIN R. YOUNG CFA, APRIL 12, 2004

With InFuse® (BMP 2) selling at a rate of $1 million per day for Medtronic's Sofamor Danek subsidiary, the news that Stryker Corporation has received approval to sell OP-1 (BMP 7) for spinal indications is significant news.

Three years ago, OP-1 (a bone morphogenic protein better known as BMP 7) was granted a humanitarian device exemption for use in non-union long bone fractures. And even that approval came with the limitations that OP-1 was indicated only where use of autograft is unfeasible and alternative treatments have failed. Bottom line; it's indicated for just a few thousand patients. Small market. Small win. Ok, next.

And next was InFuse® - indicated specifically as a substitute for autograft. Priced at around $5,000 per patient it set a number of new standards - not the least of which, figuring out how to pay for it. The answer: don't do the autograft second surgery (cost also around $5,000) and slap on a bone growth stimulator post-surgery.

InFuse® is a massive amount of bone morphogenic protein. A literal vial of fluid is injected into a collagen sponge which, when implanted in a metal cage stimulates bone growth. But a significant amount leaches out. Where autograft requires mere picograms of growth factor to achieve fusion, InFuse®, in a collagen sponge, requires several hundred times that amount to work. WHere's all of it going? Answer: out. It's not a problem but surgeons are finding ways to control the elution rate of InFuse® and achieving super results. Off-label, but so what, getting more from less is a problem?

Which brings us to Stryker's newly approved OP-1 for the spine. Unlike InFuse®, OP-1 is in a putty (a collagen carrier and a handling excipient). Elution rates will be, in our opinion, different than InFuse® which is essentially squirted into a collagen sponge. The indication is revision spine surgery. Failed spine surgery. Patients are likely to be smokers, diabetics or are suffering from osteoporosis who've had failed spinal fusions.

Again, Stryker went for the humanitarian device exemption. By definition that means a population of less than 4,000 patients. Still, Medtronic's Sofamor Danek has 'infused' the market with a new confidence and ethos of experimentation when it comes for BMPs. Mark it down, surgeons will use OP-1 for spine surgery, on label and off.

At this past March's AAOS meeting a three-arm study conducted by Blattert, Delling, Dalal, et al. (two universities in Germany and a Stryker employee) was presented which compared hydoxyapatite cement doped with OP-1 to plain old autograft. And then, for fun, the researchers threw in one arm of the study with hydroxapatite cement but with no OP-1. The test subjects were 36 sheep - 12 in each arm of the study (what human would agree to be randomized in this manner?). The end point was spinal fusion. The results:

Autograft: fusion in 1/10 sheep

Hydroxapatite but NO OP-1: fusion in 2/12 sheep

Hydroxapatite w/ OP-1: fusion in 10/12 sheep

Not only did OP-1 show statistically significant healing, but it avoided the morbidity of an autograft harvest.

Ongoing OP-1 studies include a 238 patient study at 24 sites. Enrollment is done. These are patients diagnosed with degenerative spondylolisthesis (Grades I/II) and symptomic spinal stenosis. The patients will be randomized 2:1, meaning that for every two patient treated with OP-1 putty, one will receive autograft. Dr. James Farmer, one of the study's lead investigators and an attending Spine Surgeon at the Hospital for Special Surgery (HSS) in New York (HSS is an investor in HealthpointCapital) commented about the study as follows, 'As our lifespan continues to grow longer, spinal stenosis will inevitably become more and more common. OP-1 enables us to offer a treatment that eliminates a second surgical site. As a result, the operation has less postoperative pain and shorter surgical time.'

Additionally, the study will be looking at older patients (typically under 81 years of age) who are experiencing severe pain in their lower back and legs due to degenerative lumbar spondylolisthesis with spinal stenosis.

As many as 400,000 patients in the U.S., most over 60 years of age, have these symptoms.